1. Field of the Invention
The invention is directed to a folding boom having three sections that are pivotally coupled to one another and in particular to a folding boom used as a row marker for an agricultural implement having an extended working position and a retracted transport position.
2. Description of Related Art
Row markers are commonly attached to agricultural implements, such as planters and grain drills, to mark the field for the farmer's next pass. As implements have become wider row markers have become longer. The longer row markers have folded transport positions and extended working positions.
As agricultural implements became wider, tri-fold markers were developed having three pivot points, see U.S. Pat. Nos. 4,207,950, 4,449,590, 4,986,367 and 5,379,847. In all three above-identified tri-fold designs, a single hydraulic cylinder is used to manipulate the folding and unfolding action of the row marker. In the first two designs, U.S. Pat. Nos. 4,207,950 and 4,449,590, a cable or chain is used to extend the outboard segment during an unfolding operation. The cable or chain does not control the movement of the outboard segment during the folding cycle, creating a high kinetic impact when the outboard segment engages a stop located on the middle segment. In U.S. Pat. No. 4,986,367, a control arm is used to extend the outboard segment. In U.S. Pat. No. 5,379,847 the segments of the boom rotate simultaneously when folding and unfolding.